Reset solutions for performance limitations induced by Coulomb friction in a motion control system with a disturbance observer

In a proportional-integral-derivative (PID) motion control system under Coulomb friction, a suitable reset of the integral action was recently shown in [1] to reduce significantly the settling time. Motivated by the benefits of disturbance-observer schemes (DOB) over PID schemes, we show that the DOB scheme is prone to an analogous performance limitation in the presence of Coulomb friction and extend then the reset strategy in [1] for the DOB scheme. The working principle and the effectiveness of the solution is illustrated in simulations.